The embodiments disclosed hereinafter generally relate to systems and methods for determining pitch and power settings during flight when the air data system is detected to be unreliable or failed.
Modem commercial aircraft have increasing demands for availability and integrity of air data. Air data describes the air mass state of an aircraft around the aircraft during flight. This air data is used by pilots and on-board systems to make operational decisions and control actions regarding an aircraft. This air data may include, for example, pitot or total pressure, static pressure, angle of attack, angle of sideslip, and other suitable air data. Conventional sensors used to measure this type of data may be adversely affected by environmental conditions or other conditions or events. For example, ice or other foreign materials may prevent an accurate measurement of pressure by a pitot tube used to measure total pressure.
A pitot tube is a pressure measurement instrument used to measure fluid velocity. The measured pressure is the stagnation pressure of the air, which is also referred to as total pressure. Static pressure is the ambient air pressure at the present vehicle altitude, and total pressure is the sum of the static pressure and the impact pressure due to vehicle forward velocity. This measurement, together with static pressure measurements measured using static port sensors on the side of the fuselage, may be used to identify the impact pressure. The impact pressure may then be used to calculate an airspeed of the aircraft.
Signal processing circuits, based on pressure signals supplied from the pressure sensors, determine and supply signals representative of various flight-related parameters. In some applications, sensors and associated processing circuitry have been packaged together into what may be referred to as an air data module.
Air data systems provide airplanes with airspeed, altitude and vertical speed information. When conditions of unreliable or failed air data exist, the flight crew is presented with erroneous and conflicting information that can lead a crew to put the airplane into a potentially unsafe operating condition.
Unreliable or failed air data (altitude and/or airspeed) system events on commercial airplanes can result in an accident due to the flight crew's inability to recognize the failure, and/or inability to maintain a safe flight condition following the failure. These unreliable air data events can be a result of flight through volcanic ash, icing, birds or bugs, maintenance activity in which the airplane was not properly returned to flight worthy status (e.g., tape was not removed from static ports), or other faults. When these events occur at night, without external visual references, this exacerbates the difficulty in maintaining spatial orientation because flight-critical instruments are unavailable or erroneous.
When a pilot recognizes that the air data is unreliable, their training (reaching back to their general aviation training) requires the pilot to fly pitch and power. That is, transition from pulling (or pushing) on the control column to obtain a specific vertical speed (erroneous in these failures), to examining the pitch (how high the airplane is pointed above or below the horizon) and the power setting. Pilots have a conceptual idea of what combination of pitch/power is appropriate, and what is inappropriate. For example, if the airplane is pointed below the horizon toward the ground, and its thrust level is high, then regardless of what the onboard instruments show, the airplane must be accelerating. Recognizing that the instruments are erroneous and establishing a safe, known pitch and power configuration is crucial to keeping the airplane from entering a steep dive, or an excessive pitch up condition, which can lead to a stall.
U.S. Patent Application Publ. No 2010/0100260 A1 discloses a monitor for comparing primary air data with alternative (i.e., synthetic) air data for the purpose of determining whether the primary air data can be relied upon for performing operations with respect to the aircraft. The disclosure of US 2010/0100260 A1 is incorporated by reference herein in its entirety. For the purpose of the filing of patent applications claiming priority to the instant application, in countries which do not accept incorporations by reference, this disclosure includes a drawing (see FIG. 8) and associated written description taken directly from US 2010/0100260 A1.
There is a need for systems and methods for displaying pitch- and power-based guidance commands and flight path information in an intuitive manner after the occurrence of an unreliable or failed air data (altitude and/or airspeed) system event.